Performance venues such as theaters, arenas, concert halls, auditoriums, schools, clubs, convention centers, and television studios can employ battens or trusses to suspend, elevate, and/or lower lighting, scenery, draperies, and other equipment that can be moved relative to a stage or floor. Such battens can include pipe or joined pipe sections that form a desired length of the batten. Battens can be 50 feet or more in length. To support heavy loads or suspension points are that spaced apart, for example, 15-30 feet apart, the battens may be fabricated in various configurations, such as ladder, triangular, or box truss configurations. A number of elevating or hoisting systems are available for supporting, raising, and lowering battens and/or articles used in such venues.
Battens can be counterweighted in order to reduce the effective weight of the battens and any associated loads. As a result, the power necessary to raise and lower battens can be reduced. However, conventional counterweight systems can represent a significant cost, with respect to both equipment required and time involved to install such equipment.
Some conventional elevating or hoisting systems can employ a winch to raise and/or lower battens and other articles. Such winches can be hand-operated, motorized, and/or electrically powered. Other conventional elevating or hoisting systems can utilize a hydraulic or pneumatic device to raise and/or lower battens.
Conventional elevating or hoisting systems can include a locking device and an overload limiting device. In a sandbag counterweight system, for example, the locking device may be merely a rope tied off to a stage-mounted pin rail. The overload limit can be regulated by the size of the sandbag. In such a rigging design, however, a number of additional bags can be added to the set of rope lines, and thereby exceed the safe limit of suspension ropes and defeat the overload-limiting feature.
Elevating or hoisting systems that utilize winches can employ a locking mechanism, such as a ratchet lock mechanism. When such winches are heavily loaded, the locking capacity of the ratchet lock, or other locking mechanism, can be overcome, resulting in the suspended load being dangerously dropped. As a result, conventional lift systems can have less than effective safety mechanisms.
In addition, conventional lift systems may be configured such that a pulley, or loft block, mechanism is attached directly to an overhead building support. As a result, an undesired amount of horizontal stress can be placed on the overhead building supports to which the system and associated load are attached.
Ropes or cables utilized to raise and/or lower a batten or other load may be wound about and unwound from a drum connected to a lift system motor. In conventional lift systems, the cables may rub unevenly against adjacent cables as they are being wound about and unwound from the drum. Such uneven rubbing can cause friction that may increase the rate at which the cables, drum, and other components need to be serviced and/or replaced. In addition, such friction can cause increased noise that may be undesirable in certain performance environments.
Some conventional drums can have a size and/or coil cables about the drums such that a large space is needed in which to locate the drum in or about the lift system. In “yo-yo” type drums and “pile” type drums, cables coil about the drum vertically on top of themselves. For example, in a “pile” type drum, after the cable has wound completely across the face of the drum, it is forced up to a second layer at a flange on the side of the drum. The cable then winds back across the drum in the opposite direction. In order to advance across the drum, the cable must cross over two cable “notches” of the previous coil. Such “cross-over” subjects a cable to abrasion, crushing, and pinching as it is pushed over the two cable notches across the crown of the first cable layer. Such stress can cause erratic motion of the cables as they are wound up onto the drum and/or unwound from the drum. Such vertically stacked coils of cables in conventional drums contribute to the need for increased torque to wind and unwind cables on those drums.
Conventional lift systems can include a cable management system in which electrical wires in a cable are stacked in layers back and forth on top of each other. Such cable management systems risk pinching and/or binding of the cable (and wires).
Thus, there is a need for a lift assembly drum that can wind and unwind cables in a smooth and controlled manner so as to minimize friction and noise. There is a need for a lift assembly drum that can occupy a relatively small space. There is a need for a lift assembly drum that has a decreased need for torque and is thus more energy-efficient. There is a need for a lift assembly system that includes a cable management system that avoids unnecessary pinching or binding of electrical and/or other wires or cables as a load is raised and lowered.